Subject: Re: [syzbot] general protection fault in security_inode_getattr

From: syzbot <[email-masked]>
Date: Sat, 15 Oct 2022 10:24:38 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    55be6084c8e0 Merge tag 'timers-core-2022-10-05' of git://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=147637c6880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df75278aabf0681a
dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1585a0c2880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1480a464880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6c791937c012/disk-55be6084.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cb21a2879b4c/vmlinux-55be6084.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2d56267ed26f/mount_1.gz

The issue was bisected to:

commit 35697c12d7ffd31a56d3c9604066a166b75d0169
Author: Yonghong Song <[email-masked]>
Date:   Thu Jan 16 17:40:04 2020 +0000

    selftests/bpf: Fix test_progs send_signal flakiness with nmi mode

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13032139900000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=10832139900000
console output: https://syzkaller.appspot.com/x/log.txt?x=17032139900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: 35697c12d7ff ("selftests/bpf: Fix test_progs send_signal flakiness with nmi mode")

general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 0 PID: 3761 Comm: syz-executor352 Not tainted 6.0.0-syzkaller-09589-g55be6084c8e0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
FS:  00007f246f27e700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f246f27e718 CR3: 00000000717a9000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 vfs_getattr+0x22/0x60 fs/stat.c:158
 ovl_copy_up_one+0x12c/0x2870 fs/overlayfs/copy_up.c:965
 ovl_copy_up_flags+0x150/0x1d0 fs/overlayfs/copy_up.c:1047
 ovl_maybe_copy_up+0x140/0x190 fs/overlayfs/copy_up.c:1079
 ovl_open+0xf1/0x2d0 fs/overlayfs/file.c:152
 do_dentry_open+0x6cc/0x13f0 fs/open.c:882
 do_open fs/namei.c:3557 [inline]
 path_openat+0x1c92/0x28f0 fs/namei.c:3691
 do_filp_open+0x1b6/0x400 fs/namei.c:3718
 do_sys_openat2+0x16d/0x4c0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_open fs/open.c:1334 [inline]
 __se_sys_open fs/open.c:1330 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1330
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f246f2f2b49
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f246f27e2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f246f3774b0 RCX: 00007f246f2f2b49
RDX: 0000000000000000 RSI: 0000000000000300 RDI: 0000000020000140
RBP: 00007f246f3442ac R08: 00007f246f27e700 R09: 0000000000000000
R10: 00007f246f27e700 R11: 0000000000000246 R12: 0031656c69662f2e
R13: 79706f636174656d R14: 0079616c7265766f R15: 00007f246f3774b8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
FS:  00007f246f27e700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005643c9471000 CR3: 00000000717a9000 CR4: 0000000000350ee0
----------------
Code disassembly (best guess):
   0:	48 89 fa             	mov    %rdi,%rdx
   3:	48 c1 ea 03          	shr    $0x3,%rdx
   7:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   b:	0f 85 04 01 00 00    	jne    0x115
  11:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  18:	fc ff df
  1b:	49 8b 5d 08          	mov    0x8(%r13),%rbx
  1f:	48 8d 7b 68          	lea    0x68(%rbx),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 d7 00 00 00    	jne    0x10b
  34:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  3b:	fc ff df
  3e:	48                   	rex.W
  3f:	8b                   	.byte 0x8b